1. Field of the Invention
This invention relates to packages for optical semiconductor devices, especially a package for optical semiconductor devices that are excellent in high frequency characteristics.
2. Description of the Background Art
In recent years, the transmission rate is accelerated one after another from 600 Mbps to 2.5 Gbps, moreover to 10 Gbps, in the field of optical communications. Therefore, the light emitting devices and the photo detectors for optical transmitter-receivers are required for quick-operating. With this, good high frequency characteristics and low cost are required for the packages of the light emitting devices and the photo detectors. There are a stem type package in coaxial form having a simple structure and a butterfly type package using a strip line in box form for the light emitting devices and the photo detectors.
The conventional stem package includes a stem-body 113, as shown in FIG. 9A and FIG. 9B. A pair of lead terminals 105 for photodiodes and a lead terminal 112 for signal supply are inserted in respective through holes of stem-body 113 and insulated by glass 106. Moreover, a sub-mount 102 and a mount 901, in which a semiconductor laser 103 is mounted, adjoins the lead terminal 112 for signal supply on the upper surface of the stem-body 113, and a recess 109, in which sub-mount 108 and the photodiode 107 for monitoring are attached, is located at the upper surface of stem-body 113. Here, the recess 109 is located where the laser light from the monitor face, opposite to light emitting face of the semiconductor laser diode, is input into the photodiode 107 for monitoring, mounted on sub-mount 108. In addition, an earth lead terminal 114 is attached as in FIG. 9A.
A semiconductor laser 103 is mounted on one side of mount 901 with sub-mount 102 between them, the photodiode 107 for monitor is mounted on the recess 109 with sub-mount 108 between them and then the predetermined lead terminals are connected with a wire 104,110,111. Thereby, a semiconductor laser device having the stem formed as mentioned above is constituted (for example, U.S.P. non examined publication No. 2002/0041612A1, and 2002/0141142A1).
In the semiconductor laser device formed as mentioned above, when a voltage of about 1.5 V is applied between the lead terminal for signal supply 112 and the earth lead terminal 114, an electrical current of tens of mA flows in the semiconductor laser device and laser light is emitted. The light emitted from the face opposite to the light emitting face is detected at the monitor photodiode 107 to control the quantity of the emitted light.
Stem packages for optical semiconductor device, with good heat radiating properties for radiating the heat generated by the semiconductor laser devices, are shown in Japanese Non-examined Patent Publications No.58-98995, No.07-240565 and U.S. Pat. No. 5,262,675.
However, in the conventional package for an optical semiconductor device, although the high frequency characteristics of a butterfly package are good, it is made very expensive by the complicated structure. On the other hand, although the stem package is cheap, high frequency characteristics are not good, so it is difficult to use for high-speed transmission at 10 Gbps or more.